Collar stay



FIG. 1 is a perspective view of a collar stay showing my new design;

FIG. 2 is a right side view thereof;

FIG. 3 is a left side view thereof;

FIG. 4 is a bottom plan view thereof;

FIG. 5 is a top plan view thereof;

FIG. 6 is a rear view thereof; and,

FIG. 7 is a front view thereof. 

CLAIM The ornamental design for a collar stay, as shown and described. 